Unwanted or unauthorized email is a significant bane for users on worldwide networks, such as the current public Internet. Once a person's email address becomes known in a network system, it can easily be replicated in computerized lists and passed on electronically to an unlimited number of parties who have not been authorized or invited to send email to the user. A user's electronic mailbox can become inundated with such unauthorized email. Unauthorized or unwanted email is referred to generically in the industry by the term “spam”, although the term is not intended to be associated with or to disparage the popular canned meat product sold under the trademark “Spam” by Hormel Corp. The user may have an email address with a commercial information service provider (ISP) service which limits the amount of email that can be accepted and/or stored or which charges the user by the volume received. The user may also waste a significant amount of time opening and reviewing such unwanted email. Unauthorized email may also be sent by unscrupulous persons who may enclose a virus or noxious software agent in the email which can infect the user's computer system, or which can be used as an unauthorized point of entry into a local network system that handles the user's email.
Most, if not all, of the current software to control the receipt of spam is based upon the use of identifying lists of known spam sources or senders (“spammers”). Such conventional spam control software functions on the basis of receiving all email as authorized unless a sender is identified as being on the exclusion list and the email can be filtered out. This approach is only as good as the identifying list and cannot guarantee that the user will not receive spam. Spammer lists require frequent updating and must be distributed in a timely manner to all subscribers to the spam control software or service. Sophisticated spammers frequently change their source Internet address, and can defeat attempts to keep exclusion lists current. They can also route the unwanted email through the Internet servers of other parties so as to disguise the source of the emails through innocuous or popularly recognized names. A user's email address may also become known to large numbers of individuals in public chat rooms or on public bulletin boards. Unwanted email sent by individuals are not tracked on spammer lists, because the sending of email by individuals is technically not spamming.